Store data on if a mirror is anycasted (ipinfo)

The `ipinfo.io` database provides data on if an IP is anycast. We should store this in the database for future use (internal/publish it on the mirrors page?).

```
Anycast Information

curl ipinfo.io/8.8.8.8?token=$TOKEN

{
"ip": "8.8.8.8",
"hostname": "dns.google",
"anycast": true,
"city": "Mountain View",
...
}
```

* https://ipinfo.io/developers/data-types